chore(build): create dockerfile for release deployment

Signed-off-by: SphericalKat <amolele@gmail.com>

Dockerfile

@@ -0,0 +1,50 @@
+FROM elixir:alpine AS build
+
+# install build dependencies
+RUN apk add --no-cache build-base npm git curl py-pip
+
+# prepare build dir
+WORKDIR /app
+
+# install hex + rebar
+RUN mix local.hex --force && \
+    mix local.rebar --force
+
+# set build ENV
+ENV MIX_ENV=prod
+
+# install mix dependencies
+COPY mix.exs mix.lock ./
+COPY config config
+RUN mix do deps.get, deps.compile
+
+# build assets
+COPY assets/package.json assets/package-lock.json ./assets/
+RUN npm --prefix ./assets ci --progress=false --no-audit --loglevel=error
+
+COPY priv priv
+COPY assets assets
+RUN npm run --prefix ./assets deploy
+RUN mix phx.digest
+
+# compile and build release
+COPY lib lib
+# uncomment COPY if rel/ exists
+# COPY rel rel
+RUN mix do compile, release
+
+# prepare release image
+FROM alpine:3.9 AS app
+RUN apk add --no-cache openssl ncurses-libs libstdc++
+
+WORKDIR /app
+
+RUN chown nobody:nobody /app
+
+USER nobody:nobody
+
+COPY --from=build --chown=nobody:nobody /app/_build/prod/rel/ketbin ./
+
+ENV HOME=/app
+
+CMD ["bin/ketbin", "start"]